Exercise can slow ageing, study finds

Walking for 30 to 40 minutes three times a week appears to be all that is needed to reverse some of the effects of age. Photo / Getty Images

Moderate but regular exercise can boost the size of parts of the brain that shrink with age, according to scientists who believe light physical activity is one of the best ways of preventing senile dementia.

A study involving 120 people aged between 60 and 80 found that walking briskly for 30 to 40 minutes a day three times a week was all that it takes to re-grow the structures of the brain linked with cognitive decline in later life. The effect was equivalent to stopping the ageing clock of by between one and two years and is one of the first scientifically controlled studies showing the power of physical exercise in delaying mental decline, scientists said.

Brain scans taken before and after the year-long study showed that two regions of the brain in particular, the prefrontal cortex and the hippocampus, grew in volume among the group undertaking light aerobic exercise, while they continued to shrink in those who were given only stretching tasks.

The exercise group also did better at cognitive tasks that tested things such as memory, language ability and attention which are known to decline with age. The results suggest that brain and cognitive function of the older adults remain plastic and highly malleable. There is not this inevitable decline that we used to think there was.

We can improve brain function by relatively modest amounts of physical activity, said Kirk Erickson of the University of Pittsburgh.

Between six months and one year of regular physical activity can actually increase the size of the prefrontal cortex regions and another region of the brain called the hippocampus, he told the American Association for the Advancement of Science in Chicago. Both of these regions deteriorate and shrink as we get older. The prefrontal cortex is really involved in a lot of higher level cognitive functions and the hippocampus is well known to be involved in memory formation, and when it shrinks it leads to Alzheimer's and dementia, he said.

There is strong epidemiological evidence linking a sedentary lifestyle to an increased risk of Alzheimer's disease and dementia, but this latest study was part of a randomised, controlled trial which has a greater power of linking cause and effect, Professor Erickson said. The scientists do not as yet know what causes the brain areas to increase in volume. It might be increased blood flow or an increase in the number of neurons or other cells.

While there was a 2 per cent average increase in volume within the exercise group, the same brain regions shrank by about 1.5 per cent in the other group, which is the normal rate of shrinking, Professor Erickson said.

People who take part in moderate exercise say they feel as if the fog has lifted.

Stopping the clock

* Moderate exercise can boost the size of parts of the brain that shrink with age.* Walking briskly for 30 to 40 minutes a day three times a week was all that it takes to re-grow the structures of the brain linked with cognitive decline in later life.* The effect was equivalent to stopping the ageing clock by between one and two years.